Wrench



spt. 12, 1939. F P, KRUSE 2,172,561

WRENCH Filed June 14, 1937 I IN V EN TOR. FEEDER/cre Keus@ HIS ATTORNEY.

Patented Sept. 12, 1939 UNITED `STATES WRENCH Frederick P. Kruse, Berkeley, Calif., assignor of forty per cent to Charles 0. Bruce Application June 14; 1937, Serial No. 148,031

4 Claims'.

My invention relates to wrenches and in particular to a wrench capable of uniformly tightening nuts and the like within predetermined limits.

In the tightening of nuts it is important that the associated bolt retain at all times its normal resilience in order to assure maximum efficiency for if the nut is tightened to such an extent as to strain the bolt material beyond its elastic limits, its resilience or ability to return to normal form will be destroyed. In such case further tightening of the nut will only serve to elongate or deform the bolt with consequent reduction in holding power. v

In the automotive industry as well as in other fields it is highly important that contiguous or abutting surfaces be joined under a uniform mechanical stress.. Thus, in the installation of a compression head of an engine the stud bolts should be strained to uniform tension to prevent distortion or improper joinder of abutting surfaces.

Uniformity in the tightening of nuts by mechanics with wrenches now in common use is purely a matter of guesswork, depending principally upon the length of the wrench handle and the strength of the user. It is the general, but erroneous, belief that the more a nut is tightened, the better the result, and it is not uncomman practice for the ordinary mechanic to lengthen the handle of his wrench by means of a piece of gas pipe or.the` like in order to increase leverage, thereby making it an easy matter to so tighten the nut as to strain the bolt beyond its elastic limits.

The principal object of my invention, therefore,

is to provide a wrench for straining bolts and stud bolts to predetermined and uniformly accurate tension.

Further objects of my invention are: To provide a tension wrench that is interlocking in assembly and which requires no binding or assembly of bolts or screws; to provide a wrench of the class described which is so designed as to offer minimum interference with adjacent structure when being used; to provide in such a wrench means for indicating a predetermined stress on the arm of said wrench; and to provide a simple and inexpensive device, and yet one which will be exceeding durable and effective for the purposes for which it is designed.

The invention possesses numerous additional objects and advantages, some of which, together with the foregoing, will become apparent upon perusal of the following description of my invention. It is to be understood, however, that I do not limit myself to this disclosure of the species of my invention, as I may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

Figure 1 is a plan view of a device embodying my invention.

Figure 2 is a side elevation of the device shown in Figure 1.

Figure 3 is a view partly in section and partly in elevation, looking in the direction of the arrows 3-3 of Figure 2, but showing the clutch in disengaged position.

Considered broadly, the structure of my invention comprises a socket adapted to receive a nut or the like to effect tightening thereof. The socket is provided with an outwardly extending arm to which a power-applying lever is pivoted preferably at a point near the socket. A clutch preferably of the friction type is provided. for connecting the arm to the lever at a point spaced from the pivot, preferably at the end of the arm, and the clutch is so disposed and arranged as to be operable in response to a predetermined stress on the arm to indicate such stress. Means is further provided for adjusting the clutch to respond to any desired stress on the arm, and a scale associated with said adjusting means is also provided for visually indicating desired adjustinents.

In greater detail and with reference to the preferred embodiment illustrated in the drawing, the structure of my invention comprises a socket or nut-gripping member 4 having an outwardly extending arm 5 to which a power-applying lever 6 is pivotally connected, preferably adjacent the socket, by means of a pivot 1 which is received in an aperture 8 formed in the arm.

I provide lever 6 with a hollow barrel 9 and an offset extension II, the latter forming a handle which may be grasped by the operator. Barrel 9 is preferably provided at one end with a transverse channel I2 and a transverse groove I3 which opens into said' channel. The channel, it will be noted, is so disposed and formed as to receive and support for transverse movement across the end of said barrel, a head I4 formed on the end of arm 5. The groove, on the other hand, is so disposed as to receive the arm. It will thus be seen that the arm and lever are cooperatively interlocked without screws or bolts and that disassembly thereof can be readily effected by merely moving the lever on its pivot until the head Il is transversely withdrawn from the channel I2.

Means is provided for indicating a predetermined rotational stress on the arm. For such purpose I prefer to employ a clutch mechanism of the friction type which preferably comprises a pawl I6 disposed for longitudinal movement in barrel 9 and which is adapted to enagge with a matingv notch l1 formed in head I4 of the arm. Resilient means, preferably a loading spring I8, is provided for urging said pawl into the notch, and the compression of said spring is regulated by an adjusting screwl! disposed for threaded engagement with the barrel.

In order to maintain the lever and arm in interlocked relationship upon the release of the pawl from its mating notch, I provide the head I4 with a stop 2| against which the barrel S abuts, thereby limiting the pivotal movement of the lever relative to the arm. In operation when the pawl is released from its mating notch under a set load, the barrel and stop meet with an audible snap, thus indicating to the operator, both audibly and visually, that the nut has been tightened to strain the bolt to the predetermined tension. Re-engagement of the pawl with the notch, on the other hand, is readily and simply accomplished by a slight push on the lever in the opposite direction.

In order that the operator may accurately adjust the compression of the pawl to any predetermined load within the designed capacity of the wrench, I provide a direct reading scale 22 disposed on the lever extension Il over which an indicator 23 carried by the adjusting screw i9 is adapted to move. A suitable recess 24 is formed in the lever extension H to provide adequate clearance for movement of the indicator.

While the preferred form of my invention as illustrated in the drawing uses a single pawl and pawl spring, it is to be understood that in some instances I may desire to employ a plurality of pawls and pawl springs and this without departing from the spirit of my invention. I may also employ an arm with an offset open end or offset box for knuckle clearance, or provide an 'arm capable of receiving plain or unusual extensions or a range of sockets for engaging different size bolt nuts within the loading capacity of a specific wrench; further, the arm may be provided with any well known form of ratchet end construction common to the trade.

It is to be noted that the clutch mechanism is disposed in the assembled wrench at the point of greatest mechanical advantage and at the point where it will be subjected to minimum wear throughout the full loading range. In this connection I prefer to employ that length of arm recommended by the Society of Automotive Engineers as a means of incorporating a loading spring of pre-determined capacity suitable for applicable pressure in the range of a specific capacity wrench and yet capable of stressing the various size bolts within the specific capacity range of the said wrench. In this preferred type of arrangement the loading of the spring for the entire range of a specic capacity wrench is such that release will occur with uniform repeated accuracy in all loadings and yet without excessive pressures on the friction surfaces such as would cause incid'ent early wear. It is preferred not to exceed the said distance between the axis of the socket and the engaging pawl and pawl notch as such arrangement would result in ineiiicient loading of the spring whereby the friction clutch would not function with repeated accuracy at predetermined stress release.

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention .as set forth herein.

I claim:

1. A wrench for limiting the Ypower applicable to a nut or the like turned thereby comprising a nut socket, an arm extending laterally from said socket and terminating in an end surface forming substantially a segment of a cylinder described about an axis passing through said arm at a point close to the periphery of said socket and beyond the extent thereof, a power-applying handle pivoted to said arm at said point of location kof said axis and extending along said arm beyond said end surface, a stop member formed on said arm and extending into the rotational path of said handle from one end of said end surface, a spring mounted on said handle,

4and a pawl forced by said spring against said end surface, said end surface having a notch thereon adapted to receive said pawl, said notch being in line `with the axis of said socket, the

pawl has left said notch until said handle contacts said stop member.

2. A wrench for limiting the power applicable to a nut or the like turned thereby, comprising an arm having a nut socket at one end, a lever pivoted to said arm at the socket end thereof, and means for releasably engaging said arm and lever disposed intermediate said lever and at the end of said arm opposite its socket end, said means including a recess in the lever slid'ably receiving the adjacent end of said arm, said recess forming a guideway for said end of the arm, and a spring pressed means engaging the end of said arm in said guideway to hold the arm therein until a. predetermined strain is exerted on the wrench, said spring pressed means being retractible when the turning pressure exerted on the lever exceeds the resistance offered by said spring pressed means.

3. A wrench 'according to claim 2, wherein the releasable means is disposed in a housing integral with the lever.

4. A wrench according to claim 2, provided with means for adjusting the spring pressed means, the first of said means cooperating with an indicator scale on the lever.

FREDERICK P. KRUSE. 

